Resistor for electric discharge devices



Dec. 28, 1948. T. c. SARGENT j 2,457,734

RESISTOR FOR ELECTRIC DISCHARGE DEVICES Filed Feb. 1, 1947 INVEN TOR.

Theodore C. Sdrgent ATTORNEY Patented Dec. 28, 1948 RESISTOR FOR ELECTRIC DISCHARGE DEVICES Theodore C. Sargent, Swampscott, Mass., as-

signor to Sylvania Electric Products Inc.,

Salem, Mass., a corporation of Massachusetts Application February 1, 1947, Serial No. 725,765

7 Claims. (Cl. 315-58) This invention relates to electric dischargedevices and more particularly to electric gaseous discharge devices of the negative glow type.

An object of this invention is to provide a discharge device with a resistor ballast for control-. ling the current therethrough.

Another object is to provide a discharge device with a resistor ballast which will also function as a fuse.

A further object is to provide a discharge device with a fuse-action ballasting resistor incorported therein.

A further object is to provide a discharge device with a novel lead-wire construction which incorporates a fuse-action resistor ballast therein.

Further objects, advantages, and features will be apparent from the following specification when read in conjunction with the accompanying drawings in which:

Figure 1 shows a negative glow type discharge device with which the fuse-action resistor ballast of my invention may be employed.

Figure 2 is a detail of the two lead-wire units between which the resistor of my invention is disposed.

Figure 3 is an exploded detail of the lead-wire of my invention.

Figure 4 is a detail of the lead-wire of my invention with the resistor incorporated therein.

Figure 5 is a side elevational view, partly in section, of the mount assembly of the device shown in Figure 1.

Figure 6 is a fragmentary detail of the resistor of my invention.

My invention embodies the idea of incorporating in a lead wire of a negative glow type discharge lamp a wire-wound resistor which is designed to serve as a ballast for controlling the current flow through the lamp and as a protective fuse for the lamp circuit in case a short circuit occurs within the lamp. I have found this lead wire construction to be very advantageous when used with fluorescent decorative lamps, such as Christmas tree lamps, for example. However, it will be readily apparent to those skilled in the art that this lead wire construction may readily be adapted advantageously to other forms of electric discharge devices without departing from the spirit of my invention.

The lead wire which incorporates the fuseaction resistor ballast of my invention and the manner in which it is assembled is shown in Figures 2, 3, and 4. The assembled lead-wire comprises a nickel wire member I, a dumet wire member 2, a nickel ribbon 3, a resistor I, a

nickel ribbon 5 and a copper wire member 6. In assembling these several members which comprise the composite lead wire, I prefer to assemble the nickel ribbons and Wire members into two separate units 1 and 8 and then incorporate the resistor 4 therebetween. Unit 1 comprises the nickel wire member I, the dumet wire member 2 joined to one end of the nickel wire member, and the nickel ribbon 3 mounted on thefree end of the nickel wire member 2. Unit 8 comprises the nickel ribbon 5 mounted on an end of the copper wire member 6. In mounting the nickel ribbons 3 and 5 on the ends of the nickel wire member 2 and the copper wire member 6 respectively, I have found it advantageous to edge weld the nickel ribbons, at or about the center of their longitudinal edges, to the wire members. Although I prefer to join these several elements to each other by welding, other conventional means may be employed without department from the spirit of my invention.

The flat nickel ribbons 3 and 5 are then formed into a U as shown in Figure 3 to receive the ends of resistor 4. The nickel ribbons are then clamped on the resistor, thus completing the assembly of the several elements which comprise the unitary lead wire of my invention.

Although I prefer to use nickel ribbons 3 and 5, clamped to the resistor 4, and welded to the nickel wire member 2 and the copper wire member 6 respectively, I have found that other means may be employed in incorporating the resistor in the composite lead wire. For example, blind eyelets of nickel or other noncorrosive conducting material may be crimped on the ends of the resistor in place of the nickel ribbons and the wire members welded to the centers of the eyelets. The incorporation of the resistor in the composite lead wire may also be accomplished by spraying a metal cap on the ends of the resistor and welding wire members 2 and 6 thereto.

The resistor 4 which is designed to serve as a ballast for controlling the current flow through the lamp and as a protective fuse for the lamp circuit in case a short-circuit occurs within the lamp comprises a fiiberglas cord center 9 covered by a closely woven, tight fitting flberglas braid l0 about which the resistor Wire H is wound (Fig. 6). The fiberglas cord center 9 with its covering of flberglas braid I0 provides a heat resistant mandrel which is readily adaptable to horizontal coil winding technique. The resistor wire II which I have used is an oxide- 3 coated chromel alloy of high specific resistivity wound sufficiently close on the fiberglas mandrel to provide a resistance range of about 3200 ohms per inch of coiling. The wire which I have used is about .0013" in diameter and is wound at between 430 to 580 turns per inch, depending on the resistivity of any given piece of wire, to provide the desired ohmic resistance per inch of coiling. The effective length of the resistor 4 between the nickel ribbon 3 and 5 is about 12 mm., and the. over-all length is about 17 mm. Although I have found that this particular type and size of wire, wound closely enough to provide this specified resistance range is preferable for use with a lamp of the type described below, it will be readily apparent to those skilled in the art that the particular type and size of wire used and the turns per inch may be varied, depending on the ohmic resistance desired, without departing from the spirit of my invention.

In the process of manufacturing the wire-- wound resistor of my invention I have found it desirable to coil the wire II about a fiberglas mandrel many feet in length and then cut it into the desired lengths to provide a plurality of wire-wound resistors. In doing this, however, I have found that the coiled wire II has a tendency to unravel. To overcome this difficulty, I impregnate the wire-wound resistor with a combination of phenol-formaldehyde and alkyd resin impregnants. This not only prevents the excessive unraveling of the coiled wire H but it stiifens the mandrel, thus making it easier to cut and handle, especially when the resistor is being assembled and incorporated in the lead wire. That portion of the impregnant which remains on the outer surface of the resistor decomposes at operating temperatures of the lamp, leaving no residue and thus insuring good electrical connection through the nickel ribbons 3 and 5.

A specific type of lamp with which the novel lead wire of my invention may be employed is shown in Figures 1 and 5 and is described in detail in the co-pending application of Lowry et al., Serial No. 671,688, filed May 23, 1946, now Patent No. 2,446,157. The lamp I2 comprises a glass bulb I3, the inner wall of which may be provided with a coating of luminescent material I4. A mount I5 is sealed in the glass bulb I3. The mount I5 comprises an electrode assembly mounted on. a stem I6. The stem I6. is a glass member having an elongated throat I'l with a stem press III at the top thereof and a flared portion I9 at the bottom thereof. The stem press I8 is provided with an aperture 20 and an exhaust tube 2|, through which a connection may be made for evacuation purposes. The electrode assembly comprises electrodes 22 and 23 mounted on suitable support wires which extend upwardly from the. stem press I8.

The wires which support electrodes 22 and 23 and which provide for the connection of these electrodes to an external source of electrical energy are composite members. Electrode 22 is supported by nickel wire member I which is a part of the novel lead-wire 25 described in detail above. Electrode 23 is supported by a nickel wire member 25 which is a part of lead wire 2E.

Lead wire 26 comprises the nickel wire member 25 on which electrode 23 is mounted, a dumet wire member 2'! which is sealed in the glass stem' press IB and a copper wire member 28 through,

which a connection is made to a source of. electrical energy. The lead wire 2-1 comprises the nickel wire member I which supports electrode 22, the dumet wire member 2 which is sealed in the stem press I8, the nickel ribbon 3, the wirewound resistor 4 and the nickel ribbon 5, all of which are disposed within the throat I? of the stem I6, and the copper wire member 6 through which a connection is made to a source of electrical energy.

The convenient manner in which the wirewound resistor 4, which is a part of the composite lead wire 24, is disposed within the throat I! of the stem I6 is apparent from Figures 1 and 5. The. resistor, integrally mounted in the lead wire acts as a ballast for controlling the current flow through the lamp. It is capable of operating at high temperatures and will dissipate up to about 5 watts of electrical energy. The resistor, in addition to its ballast action, also functions as a fuse so that a short circuit occurring within the lamp,-permitting about 118 volts across the resistor, will result in a burnout Withinv 10 seconds, thus serving as a protective fuse for the lamp circuit. If some type of fuse were not provided/the lamp base would overheat and become a fire hazard. There is also a possibility that the lamp itself might explode.

The fuse-action of the resistor 4 is effected in part by the decomposition of the impregnant mentioned above. When the wire-wound resistor is. coated with a combination of phenol-formaldehyde and alkyd resin. impregnants, some of the impregnating material soaks into the center of the fiberglas mandrel and is not affected under normal lamp operating conditions. However, if a short circuit occurs within the lamp, permitting line voltage across the resistor, the abnormal heating of the resistor caused thereby will cause the impregnating material within the mandrel to decompose. The heat given off by this decomposition, in combination with the abnormal heating of the resistor wire due to the fact that full line voltage is across it will speed the heating of the. wire: to a point where it will break, thus pro viding the desired fuse action. I have found that the interval of time required to effect the fuse action can be regulated and controlled by the selection of impregnating materials. Thus, if, in a given case, it is desired to effect the fuse'action in less or' more time than about 10 seconds it can be accomplished by varying the impregnants.

In impregnating the wire-Wound resistor I have found-it particularly advantageous to impregnate the resistor first with phenol formaldehyde resin and then with an oil modified phenolatcd alkyd resin. Thev phenol formaldehyde which I have used is Resinox item a product of Monsanto Chemical Co; It comprises about to solids; less than 3% free CHZEO, less than 25% ash and has a viscosity of approximately centipoises at 25 C. The oil-modified phenolated alkyd resin which I have used is Beckosol #1326, aproduct of Reichold Chemical Inc. It comprises about 49% to 51% solids and has a specific gravity of about .950 to .960. After each impregnation. the resistor is baked at about 300 C.

Although I have found it particularly advantageous to impregnate the resistor with Resinox #468, and then with Beckosol #1326, other matcrials possessing the same or similar characteristics may be employed without departing from the spirit ofmy invention. For example, the material used in the first coat is preferably one which; is slow to decompose and which will serve as a stiffening. agent to facilitate handling. and

processing of the mandrel. The material used in the second coat is preferably one which will decompose rapidly and which will serve as an adhesive agent to make the resistor Wire stick to the mandrel,

After the impregnated resistor has been incorporated in the lead wire and the lead wire, in turn, incorporated in a discharge device of the type described above, the material used in the second impregnation coating will decompose during processing of the device, leaving only the first impregnant. This impregnant will not decompose at the normal operating temperatures of the device. However, when a short-circuit occurs within the device, the abnormal heat generated thereby will, in combination with the heat from the overheated resistor wire, cause the impregnant to decompose and aid in effecting the fuse action of the resistor.

The impregnation of the resistor may be effected by applying the first coat of impregnating material to the mandrel before the resistor wire is wound thereon and then applying the second coat after the first coat has been baked and the wire wound on the mandrel. On the other hand, both impregnating materials may be applied after the resistor wire has been wound on the mandrel.

What I claim is:

1. A lead wire for an electric discharge device comprisin an electrode-supporting member, a Wire member having one end thereof connected to the electrode-supporting member, a conducting ribbon mounted on the other end of said wire member, a wire-wound resistor having one end thereof connected to and held by said conducting ribbon, a second conducting ribbon secured to the other end of said resistor, and a circuit-connecting member secured to said second conducting ribbon.

2. A lead wire for an electric discharge device comprising an electrode-supporting member, a wire member having one end thereof connected to the electrode-supporting member, a conducting ribbon mounted on the other end of said wire member, a wire-wound ballasting resistor having one end thereof connected to and held by said conducting ribbon, a second conducting ribbon secured to the other end of said resistor, and a circuit-connecting member secured to said second-conducting ribbon.

3. A lead wire for an electric discharge device comprising an electrode-supporting member, a wire member having one end thereof connected to the electrode-supporting member, a conducting ribbon mounted on the other end of said wire member, a wire-bound, fuse-action ballasting resistor having one end thereof connected to and held by said conducting ribbon, a second conducting ribbon secured to the other end of said resister, and a circuit-connecting member secured to said second-conducting ribbon.

4. A resistor comprising a fiberglas cord mandrel, a fiberglass braid wound on said mandrel, and a wire 01 high specific resistivity wound on said braid.

5. A resistor comprising a fiberglas cord mandrel, a fiberglas braid wound on said mandrel, and an oxide-coated wire of high specific resissistivity wound on said braid.

6. A resistor for an electric discharge device, said resistor comprising a fiberglas cord mandrel, a fiberglas braid wound on said mandrel, a wire of high specific resistivity wound on said braid, and a resinous material impregnated in said mandrel, said resinous material being unaffected under normal operating conditions of said device but decomposable under abnormal operating conditions.

7. A resistor for an electric discharge device, said resistor comprising a fiberglas cord mandrel, a fiberglas braid wound on said mandrel, an oxide-coated wire of high specific resistivity wound on said braid, and a resinous material impregnated in said mandrel, said resinous material being unafiected under normal operating conditions of said device but decomposable under abnormal operating conditions.

THEODORE C. SARGENT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

